tdat04622 ETC-unknow, tdat04622 Datasheet - Page 134

• Manufacturer Part Number: tdat04622
• Description: Tdat Sonet/sdh 155/622/2488 Mbits/s Data Interfaces
• Manufacturer: ETC-unknow

TDAT042G5 SONET/SDH
155/622/2488 Mbits/s Data Interface
Interface Description
Loopback Operation
Figure 32 illustrates the different types of loopback provided in the device. Loopback is controlled by core register
0x0012, loopback control (see register description on page 151).
In the following description, only the data path from Terminal A to B is discussed, but the same terms apply to the
reverse direction.
Near-End Loopback
The packet/cell payload is looped back to the data source (Layer 2 device) as soon as it crosses the Layer 1 to
Layer 2 boundary (UTOPIA block).
Far-End Loopback
The packet/cell payload is looped back to the facility (optical) data source as soon as it enters the UTOPIA block of
Terminal B. The data does not enter the Layer 2 device. The total delay from receive data input to transmit data
output in far-end loopback (FELB) mode is approximately 2 µs.
Terminal Loopback
The SONET/SDH signal is looped back at the terminal (line interface) block, and is returned to the Layer 2 device.
For terminal loopback of UTOPIA ports B, C, or D to function, UTOPIA port A must be provisioned for terminal loop-
back. This is because only the Tx clock from port A is used in terminal loopback mode.
Facility Loopback
The facility (optical) data signal is looped back to the facility as soon as it enters the Terminal B line interface block.
SONET facility loopback is only available in STS-3/STM-1 and STS-12/STM-4 modes.
106
END
FAR
SINK
CONT
TERMINAL B
(continued)
FACILITY
Figure 32. Loopback Operation
FACILITY
(OPTICS)
TERMINAL A
TERMINAL
CONT
Agere Systems Inc.
NEAR
Data Sheet
END
May 2001
5-7061(F)r.4